The present invention has for its object a process and installation for the detection of a fluid leak in a pipe sub-divided into sections sealable by a series of isolating valves arranged at each end of a section. According to this process a comparison is constantly made between the value of a pressure difference resulting from the difference between a reference pressure and the true pressure in the pipe and a predetermined pressure difference threshold value and as soon as the pressure difference threshold is passed by the true pressure difference a new comparison cycle starts between the true instantaneous pressure difference on the one hand and the said pressure difference threshold value on the other hand and the closing of the isolating valves of the pipe sections in question is initiated if the threshold value is again passed during a predetermined time starting from the beginning of the new comparison cycle.
Such a detection process is known from French Patent No. 1,482,085. For establishing the true pressure difference this known process uses a reference pressure supplied by a pressure source constituted for example by a vessel and connected on the one hand to the intake of a differential pressure gauge and on the other periodically to the pipe in such a way that the reference fluid pressure is made equal to that of the pipe whenever the threshold is exceeded. The other intake of the differential pressure gauge is connected to the pipe.